Depends on what you booked, and who you booked it through.
Thomas Cook Flights website allows you to add food as an "extra" - £6.50 for a 3 course meal with coffee.
If you booked a complete package - the meal may be included in your total package cost - best check with who you booked with. If it was through a travel agent, then they will tell you straight away, if you booked it yourself, you may need to spend some time reading small print...